The invention is concerned with an improved low profile self-ligating orthodontic bracket which may be adhesively attached to the lingual or labial surface of a tooth.
Self-ligating orthodontic brackets are known and are described, for example, in Wallshein Patents 3,052,028 and 3,724,074 as well as in other patents. Rosenberg Patent 4,712,999, for example, discloses a convertible self-ligating orthodontic bracket which is effective, but which involves a separate cover plate rotatable attached to the bracket base. The Rosenberg appliance makes no provision for arch wires that don't get fully engaged into the arch wire slot. A feature of the self-ligating orthodontic bracket of the present invention is its simplicity in that it involves a unitary integral construction without separate parts which are susceptible to being accidentally swallowed and which are difficult to apply. Also, if an arch wire is not fully engaged into the arch wire slot, the feature of this self-ligating bracket is that the continuous pressure applied by the bracket cover continually, progressively pulls the arch wire into the arch wire slot so the arch wire may exert its force when tightly engaged. This makes this simple self-ligating bracket active in part while the other action necessary for tooth positioning is the arch wire force itself.
As pointed out in the Rosenberg patent, there has been a steady improvement in orthodontic devices, and the trend has been to miniaturization and enhanced appearance from a cosmetic viewpoint, as well as increased simplification in the installation and removal procedures. At present, small slotted brackets are employed which are bonded directly to the labial or lingual surfaces of the teeth. A curved arch wire conforming to the patient's dental arch is formed of a special alloy, and pre-torqued by the orthodontist to produce the desired movement of the patient's teeth. This arch wire is fitted into the slots in the brackets in accordance with the prior art practice and the arch wire is tied down to each bracket by a arch wire or elastic donut. The application of the ligating wire requires considerable skill on the part of the orthodontist and long chair time for the patient. Moreover, the arch wire often must be removed from time to time for bending or replacement during the course of the treatment, calling for repetitive ligating operations and increased patient/orthodontist time.
When elastic donuts are used, they have a tendency to discolor and, in addition, they rapidly lose their elasticity. Accordingly, the efficiency of elastic donuts in securing the arch wire to the base of the bracket diminishes and they quickly become ineffective.
These foregoing disadvantages point to the desirability for each orthodontic bracket to incorporate a rapid clamping and unclamping device, that is, to be self-ligating, so that the need for ligating wires, elastic donuts and the like may be reduced, if not completely eliminated.
As mentioned above, prior self-ligating brackets conceived to overcome the foregoing problems have usually resulted in complex structures which are expensive to manufacture and contain separable parts which may accidentally be swallowed and are difficult to use. In addition to the Rosenberg patent, self-ligating brackets having separable parts are disclosed in U.S. Pat. Nos. 4,371,337; 4,077,126; 4,419,178; 3,444,621; 4,268,249; 3,327,393; and 4,355,975.
Although the self-ligating orthodontic brackets disclosed in the Wallshein patents 3,052,028 and 3,724,074 do have a unitary construction, the configuration of the orthodontic brackets has been found to be inappropriate for the firm and proper retention of the arch wire in the base portion of the bracket.
An objective of the present invention is to provide a one-piece self-ligating slotted orthodontic bracket which has a low profile for comfort, and which is constructed to have a cover which exerts a continual force on the arch wire that may not fit all the way into the slot, so that over time the cover will slowly force the arch wire firmly and positively into the slot to be firmly retained on the bracket. The bracket may be easily applied either to the lingual or labial surface of a tooth. Moreover, the orthodontic bracket of the present invention is conceived to be easily constructed. In its very simplest and basic design, it may be compared to the action of the one-piece clothespin that is spread to hold the clothesline firmly in its grip.